cam·bi·um 
(kămbē-əm)
(kămbē-əm)n. pl. cam·bi·ums or cam·bi·a (-bē-ə)
A lateral meristem in vascular plants, including the vascular cambium and cork cambium, that forms parallel rows of cells resulting in secondary tissues.
[Medieval Latin, exchange, from Late Latin cambīre, cambiāre, to exchange, of Celtic origin.]
cambi·al adj.